This invention relates to highway safety devices, and is especially directed to New Jersey type roadway barriers, both median (on road) barriers, and shoulder (side-of-road) barriers.
Median barriers are often disposed between opposing lanes of traffic on a divided highway to prevent head-on collisions. A common form of such a median barrier is the well-known New Jersey barrier. These New Jersey barriers are typically precast or poured concrete structures, somewhat bell-shaped in cross-section, and have a wide bottom to resist tipping from impact with an automobile or other vehicle, a flared lower section to engage the tire of a vehicle veering from the roadway into the barrier, and a more-or-less vertical upper section rising to a flattened barrier top. The flared lower section allows the vertical upper section to be set back far enough to provide clearance for the body of the vehicle. Consequently, if a vehicle veers into the New Jersey type barrier at a small angle, the barrier acts to turn the car back onto the roadway to prevent a possible head-on collision with vehicles in the lanes of opposing traffic.
The New Jersey type barrier works well when the traffic is mainly composed of vehicles of standard width and weight. The standard sized vehicles have a relatively wide wheelbase and are relatively heavy. Thus, when a standard size car or truck strikes a New Jersey barrier, the vehicle's tire will slip downward, rather than ride up and over the steep vertical section of the barrier, and the car or truck does not roll (flip over) or vault the barrier.
Recently, there has been a significant increase in the proportion of traffic constituted by smaller compact and subcompact cars. These smaller cars are lighter in weight and have a narrower wheelbase. There is a tendency in these smaller cars, when driven against a New Jersey type barrier, for the wheels to ride up higher onto the barrier. This can results in rolling over or flipping of the vehicle when striking the barrier. If a compact or subcompact car strikes the barrier at certain angles and at higher speeds, the car can completely or partially vault the barrier.
The top of the New Jersey type barrier is generally smooth with no means provided thereon for redirecting the wheel of a vehicle downward and toward the roadway to prevent flipping or rolling of the vehicle, and to prevent the vehicle from vaulting of the barrier.